Bad news for speed camera haters: This traffic researcher says they make roads safer

The city of Phoenix recently put speed cameras back on city streets — 17, to be exact.

As of last week, they went off nearly 290,000 times. More than 80,000 citations have been issued, according to the city of Phoenix. Nearly 7,700 have been paid.

And, if you really don’t like them, you can vote to ban them in November. Proposition 319 would ban the use of photo radar for traffic enforcement by state and local governments. If a company already has a contract for photo radar, they could only continue it if voters approve.

So, we decided to go to an expert to find out the real question behind all of this political debate: Do they work? Do they slow people down? Prevent crashes?

Dr. Hesham Rakha is the director of the Center for Sustainable Mobility at Virginia Tech University. The Show spoke with Rakha, beginning with that central question: Do speed cameras work?

Full conversation

HESHAM RAKHA: So, I guess the answer to that is, generally speaking, yes, they work. They reduce speeds and they reduce the accidents. The results vary depending on the site and so forth. So, there are studies like there was one study, a Cochrane review, that looked at 35 studies and they found that, for example, there were reductions near the camera sites of 8% to 49% in all crashes.

LAUREN GILGER: Wow.

HESHAM RAKHA: 8% to 50% in injury crashes and 11% to 44% in fatal crashes. This was a study in 2010. And so, there are reductions and definitely they do reduce crashes, but then it’ll depend on the location and enforcement and so forth.

LAUREN GILGER: Right. So, let’s talk about that. In terms of reducing speeding, reducing crashes as a result of speeding, do we know what kinds of collisions go down because of these cameras? There’s always this question people will say, “Do people slam on their brakes when they see a camera there and then cause more accidents?”

HESHAM RAKHA: That’s a good thing, and that leads into these variable speed limits because basically if you are driving on a freeway and you have what we call shockwaves — are you familiar with a shockwave?

LAUREN GILGER: No, what does that mean?

HESHAM RAKHA: So, a shockwave is basically you’re driving and then suddenly the car ahead of you is slamming on its brakes, and then you have to slam on your brakes. And it causes these what we call stop-and-go waves in the traffic stream. Those are extremely dangerous because you can result in rear-end crashes.

And so, one way that we as researchers are trying to reduce the speed of these shockwaves is by changing the speeds more gradually upstream to absorb those shockwaves. And you see these more cautious drivers that keep a longer gap — I mean, I look at myself as a driver. When I experience one of these shockwaves, I become more cautious and I leave a longer gap between me and the vehicle ahead of me in order to absorb any abrupt speed reduction from the vehicle ahead of me that I could then drive more safely.

LAUREN GILGER: So, cities should maybe put a notification 100 yards before the speed camera, that kind of thing? I think we do have something like that here in Phoenix.

HESHAM RAKHA: Yes, and my understanding — this is in Virginia, but I don’t know if it’s in every state — but by law, they have to put a warning sign to inform drivers that there are cameras.

LAUREN GILGER: So, overall, these work, you say, based on the research. But what do you say to critics who say these speed cameras are unfair, they’re essentially an illegal tax? We’ve seen major pushback against speed cameras in Phoenix, including a worker was shot who was fixing one once years ago here.

HESHAM RAKHA: I mean, definitely there is legitimate concern about trying to just use these as means to get tickets and income, and you see that in a lot of places. But the results show that they do reduce crashes, so in my opinion, it’s a good strategy, but as long as it’s not driven by profits, I guess.

LAUREN GILGER: And that is a sentiment that can feel like that’s what’s happening from the public’s point of view, for sure, sometimes.

HESHAM RAKHA: That’s correct. Even me as a person who drives, I feel that sometimes. I do also work on running of red lights and the design of yellow timings. And once I was driving my car and it was yellow and I tried to beat the yellow light, but it turned red on me, I got caught. And I told the guy, “I actually do studies on this.”

And so, this is what we call the dilemma zone. So, you are faced with a decision that you have to make in a very short period of time. “Do I have enough time to get through the light or do I slam on my brakes?”

Stopping is not always the right decision. If you slam on your brakes like you mentioned, I could be causing a rear-end crash with the vehicle behind me. And so, there are times where you should be running the yellow light, you should not be stopping, and there are times when you should be stopping. And so, that dilemma or decision zone is where the driver can make a wrong decision and you think that you have enough time, but you don’t.

LAUREN GILGER: Yeah, that makes a lot of sense. So, you study various parts of these kind of traffic issues. If the goal overall is to reduce speeds and to reduce the crashes and fatal crashes that come as a result of that — we have a high rate of fatal crashes on freeways in particular in Arizona, but I think on street roads as well — what else is effective? What should cities be looking at if not speed cameras, or should it be speed cameras and other things?

HESHAM RAKHA: So, studies have shown that it’s more the speed variability that is a bigger issue than the speed per se. So, if you look at, for example, trucks, here in Virginia we have these — we’re in the mountains and so the trucks travel slower than the regular vehicles given that they’re much heavier. That’s why we have truck climbing lanes in order to separate these trucks from the regular traffic. Once the speed of a vehicle goes lower than the regular traffic stream speed by about 10 miles an hour, then it becomes a safety hazard.

And so, the speed variability both spatial and temporal — like spatial meaning that we mentioned about these shockwaves, like suddenly the car ahead of you slams on their brakes that causes this propagation of the shockwave that I have to slam on my brakes, or spatial could be across the lanes where you have trucks traveling slower than cars — that is actually a bigger issue than the speed per se.

LAUREN GILGER: That’s very interesting. There was just a recent AAA Foundation study that came out here in Arizona showing that 55% of Arizona drivers think that keeping up with the flow of traffic — that “flow of traffic” phrase that you hear — is safer than actually following the speed limit. Does your research point to that being true, essentially?

HESHAM RAKHA: I guess it depends on how fast are these cars driving than the speed limit. So, if they’re driving like five to seven miles an hour above, then I would say that argument would be correct. But if it’s much higher than the speed limit, then the speed limit is there for a reason. Sections of roadway that are designed, like the curves are designed for certain speeds, so if you drive much faster than those speeds, you’re a safety hazard as well.

So, I think it’s a — I don’t think there’s a fixed answer to that. I mean, it depends on what level of speed they’re driving at relative to the speed limit and if it’s straight versus curved and so forth.

LAUREN GILGER: Yeah. So overall, if you’re looking at a place with really high rates of speeding and high rates of speed-related crashes like we see here in Arizona, is the answer just lowering speed limits all around? We’ve seen a couple of cities in the Valley do that recently, like take everything down on specific roadways by five or 10 miles per hour.

HESHAM RAKHA: I don’t think I would agree with that. I mean, if you look at the crash rate based on the national averages in the U.S., the crash rate on a freeway is half the crash rate that you have on an arterial in a downtown area.

LAUREN GILGER: OK, so if lowering the speed limit’s not the answer, speed cameras can help, it sounds like. Do you think the answer is then — is it just driving culture? Is it having more officers on the road watching and giving out tickets in real life?

HESHAM RAKHA: I’m not sure I have an answer to that, but I think definitely speed cameras can help. I think also these other technologies, like variable speed limits, and these are really trying to reduce the variability in the speeds spatially on the roadway.

LAUREN GILGER: Which sounds like it’s the most dangerous part. Wow, OK. We’ll leave it there. That is Dr. Hesham Rakha joining us, director of the Center for Sustainable Mobility at Virginia Tech. He’s also faculty in the Department of Civil and Environmental Engineering there. Dr. Rakha, thank you so much for coming on The Show. Thanks for explaining all this to me. I appreciate it very much.

HESHAM RAKHA: Thank you very much.

MARK BRODIE: We also asked the city of Phoenix how much money it’s collected as a result of the speed cameras on city roads. Out of those roughly 81,000 citations issued, just 7,657 of them had been paid as of July 30. That brought in a total of about $1.6 million.

But the city doesn’t take in all that money. After state-mandated charges, statutory assessments, and court fees, the city took in just a little under $700,000. Then it pays the company that runs the speed cameras and for staff, and any remaining funds will be invested in the city’s Vision Zero Road Safety Action Plan. All in all, the city told us “The photo safety program was never intended to generate revenue.”